bpo-30197: Enhance functions swap_attr() and swap_item() in test.support. (#1341)
* bpo-30197: Enhance functions swap_attr() and swap_item() in test.support.
They now work when delete replaced attribute or item inside the with
statement. The old value of the attribute or item (or None if it doesn't
exist) now will be assigned to the target of the "as" clause, if there is
one.
* Update docstrings.
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index ed611c9..d8d599b 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -2119,12 +2119,15 @@
restoring the old value at the end of the block. If `attr` doesn't
exist on `obj`, it will be created and then deleted at the end of the
block.
+
+ The old value (or None if it doesn't exist) will be assigned to the
+ target of the "as" clause, if there is one.
"""
if hasattr(obj, attr):
real_val = getattr(obj, attr)
setattr(obj, attr, new_val)
try:
- yield
+ yield real_val
finally:
setattr(obj, attr, real_val)
else:
@@ -2132,7 +2135,8 @@
try:
yield
finally:
- delattr(obj, attr)
+ if hasattr(obj, attr):
+ delattr(obj, attr)
@contextlib.contextmanager
def swap_item(obj, item, new_val):
@@ -2146,12 +2150,15 @@
restoring the old value at the end of the block. If `item` doesn't
exist on `obj`, it will be created and then deleted at the end of the
block.
+
+ The old value (or None if it doesn't exist) will be assigned to the
+ target of the "as" clause, if there is one.
"""
if item in obj:
real_val = obj[item]
obj[item] = new_val
try:
- yield
+ yield real_val
finally:
obj[item] = real_val
else:
@@ -2159,7 +2166,8 @@
try:
yield
finally:
- del obj[item]
+ if item in obj:
+ del obj[item]
def strip_python_stderr(stderr):
"""Strip the stderr of a Python process from potential debug output
diff --git a/Lib/test/test_support.py b/Lib/test/test_support.py
index 0dbe02e..1e6b2b5 100644
--- a/Lib/test/test_support.py
+++ b/Lib/test/test_support.py
@@ -295,17 +295,34 @@
def test_swap_attr(self):
class Obj:
- x = 1
+ pass
obj = Obj()
- with support.swap_attr(obj, "x", 5):
+ obj.x = 1
+ with support.swap_attr(obj, "x", 5) as x:
self.assertEqual(obj.x, 5)
+ self.assertEqual(x, 1)
self.assertEqual(obj.x, 1)
+ with support.swap_attr(obj, "y", 5) as y:
+ self.assertEqual(obj.y, 5)
+ self.assertIsNone(y)
+ self.assertFalse(hasattr(obj, 'y'))
+ with support.swap_attr(obj, "y", 5):
+ del obj.y
+ self.assertFalse(hasattr(obj, 'y'))
def test_swap_item(self):
- D = {"item":1}
- with support.swap_item(D, "item", 5):
- self.assertEqual(D["item"], 5)
- self.assertEqual(D["item"], 1)
+ D = {"x":1}
+ with support.swap_item(D, "x", 5) as x:
+ self.assertEqual(D["x"], 5)
+ self.assertEqual(x, 1)
+ self.assertEqual(D["x"], 1)
+ with support.swap_item(D, "y", 5) as y:
+ self.assertEqual(D["y"], 5)
+ self.assertIsNone(y)
+ self.assertNotIn("y", D)
+ with support.swap_item(D, "y", 5):
+ del D["y"]
+ self.assertNotIn("y", D)
class RefClass:
attribute1 = None
diff --git a/Lib/test/test_tempfile.py b/Lib/test/test_tempfile.py
index 51df1ec..d0cf04b 100644
--- a/Lib/test/test_tempfile.py
+++ b/Lib/test/test_tempfile.py
@@ -273,13 +273,12 @@
tempfile._get_default_tempdir()
self.assertEqual(os.listdir(our_temp_directory), [])
- open = io.open
def bad_writer(*args, **kwargs):
- fp = open(*args, **kwargs)
+ fp = orig_open(*args, **kwargs)
fp.write = raise_OSError
return fp
- with support.swap_attr(io, "open", bad_writer):
+ with support.swap_attr(io, "open", bad_writer) as orig_open:
# test again with failing write()
with self.assertRaises(FileNotFoundError):
tempfile._get_default_tempdir()
diff --git a/Misc/NEWS b/Misc/NEWS
index 71db0ee..026beff 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -1107,6 +1107,12 @@
Tests
-----
+- bpo-30197: Enhanced functions swap_attr() and swap_item() in the
+ test.support module. They now work when delete replaced attribute or item
+ inside the with statement. The old value of the attribute or item (or None
+ if it doesn't exist) now will be assigned to the target of the "as" clause,
+ if there is one.
+
- Issue #24932: Use proper command line parsing in _testembed
- Issue #28950: Disallow -j0 to be combined with -T/-l in regrtest
